Motorists make their way down 6th Street during a snowstorm Friday in Rapid City, S.D.

SIOUX FALLS, S.D. — Blizzards rolled into parts of Wyoming and South Dakota on Friday, bringing the snow-savvy states to an unseasonably early wintery standstill by closing highways and schools, and even forcing a tourist town to cancel its annual Octoberfest’s polka-dancing bar crawl.

A foot of snow had fallen in western South Dakota’s scenic Black Hills by early Friday, though residents were bracing for as much as 3 feet of the wet, heavy snow and wind gusts of up to 70 mph. The storm system spawned a tornado the night before in Nebraska and was threatening to push thunderstorms as far east as Wisconsin.

Julie Lee said she and fellow members of her White Rose Band are accustomed to snow, just “not for the fourth of October.” They had barely unloaded their instruments in South Dakota’s Old West casino town of Deadwood before snow started falling and closed the area’s only interstate.

“Our car is like an igloo,” said Lee, who sings and plays the clarinet and saxophone for her North Dakota-based polka band. “I’m glad we got everything out.”

Town officials decided to postpone its annual Octoberfest, including Friday night’s dancing-and-singing pub crawl and Saturday’s Wiener Dog Races and Beer Barrel Games. But Lee and her accordion-playing husband, who had planned to set up in one of the casino bars, still planned to entertain stranded guests. “You can only gamble for so long,” she said.

The typically bustling Pilot Travel Center near Rapid City, about 40 miles southwest, was like a ghost town Friday morning. Store general manager John Barton guessed that drivers were likely heeding forecasters’ warnings to stay off the roads.

The blowing snow was picking up outside the truck stop along Interstate 90, which was closed for about 30 miles thanks to a storm that was gaining strength as it moved in from Wyoming, where the interstate was also closed. Conditions were expected to deteriorate throughout the day.

“Yesterday we were really busy,” Barton said. “I think a lot of people got ahead of it.”

Although early October snowfalls aren’t unusual, a storm of this magnitude happens only once every decade or two on the Plains, National Weather Service meteorologist Steve Trimarchi said.

“I couldn’t say when the last time we’ve had one like this. It’s been quite a while,” Trimarchi said.

In Wyoming, reports of 5 to 10 inches of snow were common with higher amounts in the mountains. Hundreds of miles highways, including parts of interstates 25 and 90, were closed.

“I’ve lived in Wyoming my whole life and I’ve never seen it like this this early,” Patricia Whitman, shift manager at the Flying J truck stop in Gillette, said in a telephone interview Friday morning. “Usually the first snow is like Halloween.”

Whitman said her truck stop’s parking was full with travelers waiting out the storm.

“I know several of the businesses nearby are completely closed because they can’t even get workers into work — it’s pretty nasty,” she said.

The snow also snapped tree limbs that knocked out power lines, causing thousands of people to lose power.

Forecasters urged people trying to travel to carry survival kits and to stay in their vehicles if they get stranded.

“These are just really dangerous conditions,” Steve Rubin, of the National Weather Service, said Friday.

Large hail and powerful winds were forecast to hit northwest Oklahoma later Friday, while heavy rain settled in parts of Iowa and was expected to swoop northeast across the region into Wisconsin, where warnings were issued for dense fog.

In Nebraska, a tornado that touched down Thursday night damaged homes and businesses in several communities, knocked out power and toppled trees. But no injuries have been reported.

Motorists were being advised to stay off the roads in western South Dakota, where the I-90 were closed between Sturgis and the Wyoming border. Officials said the road will remain closed until storm conditions improve and crews are able to clear the highway.

The Department of Transportation also advised no travel on some other roadways in the region.